Durham University - Mathematical Sciences
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Tue, 24 Apr 2018 12:54:13 +0100Norbert Peyerimhoff: Ollivier Ricci curvature and Bonnet-Myers sharp graphs (2018-04-26 13:00:00)https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5598&seminar=5598
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5598&seminar=5598
Tue, 24 Apr 2018 12:54:13 +0100Silvia Dalla: Test Particle Modelling of Solar Energetic Particle Propagation (2018-04-27 14:00:00)Solar Energetic Particles (SEPs) are ions and electrons accelerated during flares and coronal mass ejections at the Sun. They can escape from the corona into interplanetary space and may reach near-Earth locations, where they pose a significant radiation risk to humans in space and satellite hardware. This talk will review our understanding of the origin and transport of SEPs, based on a large body of data gathered by spacecraft detectors and on theoretical models. It will focus on recent results of test particle simulations, which show that accurate modelling of SEP propagation requires a 3D approach, due to guiding centre drifts and magnetic field line meandering.https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5452&seminar=5452
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5452&seminar=5452
Fri, 23 Mar 2018 16:38:57 +0000Nicholas Young : Noncommutative manifolds (2018-04-30 16:00:00)Analytic functions of non-commuting variables are defined by abstraction from the properties of polynomial functions of tuples of matrices. Their theory has been much developed over the last decade, under the title of `free analysis' or `noncommutative analysis'.
I will describe the construction of the free Riemann surface of the matricial square root function. For this purpose one has to introduce the notion of a noncommutative manifold.
This is joint work with Jim Agler (UCSD).
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5537&seminar=5537
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5537&seminar=5537
Mon, 05 Mar 2018 14:22:28 +0000Ben Pooley: On lambda convex sets (2018-05-03 13:00:00)https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5563&seminar=5563
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5563&seminar=5563
Tue, 24 Apr 2018 12:51:51 +0100Rodrigo Ledesma-Aguilar: TBA (2018-05-04 14:00:00)https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5527&seminar=5527
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5527&seminar=5527
Tue, 19 Dec 2017 17:38:11 +0000Sanuel Borza: Localization by needles associated to a Lipshitz function on the Heisenberg group (2018-05-10 13:05:00)https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5582&seminar=5582
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5582&seminar=5582
Thu, 08 Mar 2018 10:55:37 +0000Haeran Cho: Multiscale MOSUM procedure with localised pruning (2018-05-10 16:00:00)In this work, we investigate the problem of multiple change-point detection where the changes occur in the mean of univariate data. The proposed localised pruning methodology is applicable when conflicting change-point estimates are returned with the information about the local interval in which they are detected. We study the theoretical consistency of the localised pruning in combination with the multiscale extension of the MOving SUM (MOSUM) procedure Eichinger and Kirch (2018). Extensive simulation studies show the computational efficiency and good finite sample performance of the combined methodology, which is available as an R package 'mosum'.
This is joint work with Claudia Kirch (OvGU Magdeburg).
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5211&seminar=5211
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5211&seminar=5211
Tue, 17 Apr 2018 19:36:52 +0100Yulia Meshkova: On operator error estimates for homogenization of periodic hyperbolic systems (2018-05-11 14:00:00)The talk is devoted to homogenization of solutions of periodic hyperbolic systems with rapidly oscillating coefficients. Classical results in homogenization theory looks as the convergence of solutions of the problem with rapidly oscillating coefficients to the solution of the so-called effective problem with constant coefficients. The constants in the corresponding error estimates depend on the differential operator, the lattice of periodicity, and the initial data somehow.
We are interested in the operator error estimates. In such estimates, dependence on the initial data in the error estimates is explicit: we have the norm of the data in error estimate. So, these estimates can be rewritten in operator terms.
The principal term of approximation for the solution of periodic hyperbolic systems was obtained by M. Birman and T. Suslina (2008). Our main result is approximation of solution in the energy norm. The corrector is taken into account. To obtain this approximation we have to assume that the initial data for the solution is equal to zero. The result can be written as approximation of the operator sine in the uniform operator topology with the precise order error estimate.
We use the spectral approach to homogenization problems developed by M. Sh. Birman and T. A. Suslina. The method is based on the scaling transformation, the Floquet-Bloch theory, and the analytic perturbation theory. It turns out that homogenization is a spectral threshold effect at the bottom of the spectrum.
More details: arXiv:1705.02531.https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5597&seminar=5597
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5597&seminar=5597
Tue, 24 Apr 2018 12:27:41 +0100Demi Allen: (2018-05-15 13:00:00)https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5548&seminar=5548
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5548&seminar=5548
Tue, 20 Feb 2018 09:24:39 +0000Rachael Boyd: Homological stability of groups (2018-05-17 13:00:00)https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5578&seminar=5578
https://www.dur.ac.uk/mathematical.sciences/events/seminars/?id=5578&seminar=5578
Tue, 20 Feb 2018 12:58:38 +0000